This invention relates to a methanol fuel composition, in particular, one containing a flame luminosity agent.
One of the concerns of employing methanol as a motor vehicle fuel for which it has lately attracted a good deal of attention owing to environmental considerations is that it burns with a light blue flame which readily escapes notice, particularly in daylight or a well lighted area. Because methanol burns with a practically non-luminous flame, its use as a fuel presents a safety hazard which may deter its more widespread use. So, for example, during refueling or in a collision, a methanol-fueled fire might initially go unnoticed presenting a considerable hazard to those in its vicinity.
Nigrosine, an iron-containing azine dye, has been proposed for use as a luminosity agent for fuel which burns with a non-luminous flame. However, due to its heavy metal content, i.e., iron, it is entirely impractical as a luminosity agent for methanol which is intended to be used as a fuel for internal combustion engines. A combustion product of nigrosine, finely divided iron oxide particles, is quite abrasive and may result in an unacceptable rate of engine wear. In addition, fuel additives which contain heavy metals are known to deactivate emission control catalysts.
Another known approach to imparting or enhancing flame luminosity in a methanol-based fuel is to select the hydrocarbon composition of the primer. Such primers are added at 5 to 15 percent with the primary purpose of facilitating engine starting. They may contain gasoline, toluene or reformate. While such materials do provide flame luminosity, they detract from the clean-burning properties of methanol and, as noted in European Patent Application 0 127 316, can lead to problems of water sensitivity.
Another proposal for overcoming the problem associated with the non-luminous burning characteristics of methanol has been the use of 0.5 to 10.0 weight percent trimethyl borate flame luminosity agent as disclosed in U.S. Pat. No. 4,536,188. However, the environmental acceptability of boron-containing combustion products is at present uncertain and, in addition, the characteristic green color imparted to the flame may fail to convey the presence of a hot flame.